First, here's Alexander Cockburn:
It's a notorious inconvenience for the Greenhousers that data also show CO2 concentrations from the Eocene period, 20 million years before Henry Ford trundled out his first Model T, 300 to 400 percent higher than current concentrations. The Greenhousers deal with other difficulties, like the medieval warming period's higher-than-today temperatures, by straightforward chicanery, misrepresenting tree ring data (themselves an unreliable guide) and claiming the warming was a local European affair.
We're warmer now because today's world is in the thaw following the recent ice age. Ice ages correlate with changes in the solar heat we receive, all due to predictable changes in the Earth's elliptical orbit round the sun and in the Earth's tilt. As Hertzberg explains, the clinical heat effect of all of these variables was worked out in great detail between 1915 and 1940 by Milutin Milankovitch, a giant of twentieth-century astrophysics. In past post-glacial cycles, as now, the Earth's orbit and tilt give us more and longer summer days between the equinoxes.
And Robert Higgs:
When your research implies a “need” for drastic government action to avert a looming disaster or to allay some dire existing problem, government bureaucrats and legislators (can you say “earmarks”?) are more likely to approve it. If the managers at the NSF, NIH, and other government funding agencies gave great amounts of money to scientists whose research implies that no disaster looms or no dire problem now exists or even that although a problem exists, no currently feasible government policy can do anything to solve it without creating greater problems in the process, members of Congress would be much less inclined to throw money at the agency, with all the consequences that an appropriations cutback implies for bureaucratic thriving. No one has to explain all these things to the parties involved; they are not idiots, and they understand how the wheels are greased in their tight little worlds.
Finally, we need to develop a much keener sense of what a scientist is qualified to talk about and what he is not qualified to talk about. Climatologists, for example, are qualified to talk about the science of climatology (though subject to all the intrusions upon pure science I have already mentioned). They are not qualified to say, however, that “we must act now” by imposing government “solutions” of some imagined sort. They are not professionally knowledgeable about what degree of risk is better or worse for people to take; only the individuals who bear the risk can make that decision, because it’s a matter of personal preference, not a matter of science. Climatologists know nothing about cost/benefit cosiderations; indeed, most mainstream economists themselves are fundamentally misguided about such matters (adopting, for example, procedures and assumptions about the aggregation of individual valuations that lack a sound scientific basis).